Enteral nutrition is a form of hyperalimentation and metabolic support in which nutrient formulas or medicaments are delivered directly to the gastrointestinal tract, either the stomach or the duodenum. Fluid administration and aspiration is accomplished through use of a nasogastrointestinal tube generally referred to as an enteral feeding tube as disclosed in FIG. 1. Enteral feeding is frequently utilized where adequate nutritional intake cannot be acheived through oral alimentation because of poor appetite, chronic nausea, general apathy, sedation or other symptoms or characteristics associated with serious disease. By delivering appropriate nutrient fluids directly to the gastrointestinal tract through an enteral feeding tube, nutritional and metabolic support of the patient is acheived without risk of sepsis or metabolic derangement as may occur in intraveneous hyperalimentation. Because of increasing emphasis on out-patient care, enteral nutrition has been recognized as a desirable method of hyperalimentation as it requires only oral intubation of the feeding tube rather than manipulation of sterile cannulae or other means of interconnection with surgically implanted subclavian catheters as used in parenteral hyperalimentation.
FIG. 2 discloses the design and configuration of a prior art enteral feeding tubes. A distal end of the feeding tube is provided with a multiplicity of tube openings through the tube side walls which define tube outlets. Distal to the tube outlets is an elongated weighted guide tip to facilitate intubation. Other examples of prior art enteral feeding tubes of similar design are disclosed in U.S. Pat. Nos. 4,410,320; 4,390,017; 4,270,542 and 4,388,076.
The disadvantages of such prior art enteral feeding tubes is the discomfort and intubation difficulties associated with initial insertion and passage of the blunt-ended guide tip into and through the naso-pharyngeal passage. Further, the patient is exposed to the risk of internal injury should a stylet exit the tube through one of the tube outlets during intubation. Further, the prior art enteral feeding tubes have an external configuration which provide no means for utilizing peristaltic action of the esophagus to assist in intubation.
As a result of such disadvantages, we developed a uniquely designed enteral feeding tube addressing the problems of prior art tubes. Our improved tubes are disclosed in U.S. Pat. No. 4,490,143 and is also the subject of a pending continuation-in-part patent application Ser. No. 614,276, filed May 25, 1984. In the enteral feeding tube disclosed therein, a non-collapsible tube insert, generally referred to as a bolus, is disposed on a distal end of the tube. The bolus carries at least one opening defining a tube outlet and has an internal passage which is normal to the tube outlet to prevent inadvertent exiting of the stylet during intubation. In addition, the bolus of our improved enteral feeding tubes further include an enlargened external configuration to utilize esophageal peristaltic action during intubation.
However, a problem encountered in all prior art enteral feeding tubes is occlusion of the tube outlet with gastrointestinal debris and cogulated feeding material which impedes administration and aspiration of fluids through the enteral feeding tube. The outlets of prior art tubes may also become blocked by being drawn up against the mucosal lining of the gastrointestinal tract during an aspiration procedure.
Another problem encountered with prior art tubes is that the tube side walls which define the tube outlets curve toward each other as disclosed in transverse section in FIG. 2A. Because of the curvature of the side walls the flow of fluid out of the tube is restricted. More importantly, the tube outlets are perpendicular to the longitudinal axis defining the fluid stream which also restricts fluid flow. None of the prior art enteral feeding tubes gradually channel the fluid stream out of the tube outlet so as to substantially maintain the same flow rate through the outlet as is present in the tube lumen. Further, the inwardly curving side walls define a tube outlet which in transverse section has a generally frusto-conical shape as disclosed in FIG. 2A. Such an outlet is easily occluded with mucous and other gastrointestinal debris.
Many of the same problems discussed above are encountered with other types of catheters such as urethral and esophageal catheters.
The most preferred design of an enteral feeding tube or catheter would be an open-ended tube which would acheive maximum rate fluid flow out of the tube. Though preferable from the standpoint of maximizing fluid flow, an open-ended enteral feeding tube would be impractical. Such a tube would easily occlude with mucous during aspiration. Further, a distal end deflection tip or elongated guide tip could not be employed with an open-ended tube. Such distal end tips are necessary to guide tube passage and deflect the tube end from the mucousal linings of the gastrointestinal tract during intubation. As a result, an open-ended feeding tube could become entrapped or impaled against the mucousal linings making intubation extremely difficult and risking trauma to such tissue linings.
Hence, prior to the development of the present invention, a need existed for an enteral feeding tube which would not become occluded with feeding material or mucous. A need also existed for an enteral feeding tube having a design which would approximate the fluid flow rate characteristics of an open-ended tube and yet carry a distal end guide or deflection tip as known in the art.